Thermogravimetric analysis and morphological behavior of melamine‐formaldehyde filled polyvinyl acetate—Polyester nonwoven fabric composites

The objective of the present research work is to study the effect of different amounts of melamine‐formaldehyde (MF) viz., 0–20 parts by dry weight on the thermal stability of polyvinyl acetate (PVAc) latex impregnated polyester nonwoven fabric composites. From the thermogravimetric analysis, the improvement in thermal stability of the composites was noticed with increase in the MF content. Composites fabricated with five parts MF‐incorporated PVAc showed a drastic increase in the onset degradation temperature when compared with unfilled composites. It was found that the degradation of MF‐loaded PVAc‐polyester nonwoven fabric composites takes place in two steps. Degradation kinetic parameters were calculated for the composites using Broido and Horowitz‐Metzger methods. The tensile fractured composite specimens were analyzed using scanning electron microscope to know the morphological behavior. The increased percentage ash content also supports for the increased thermal stability of the composites with increasing the MF content in the system. The adhesion between the fiber and matrix can be seen from scanning electron microphotographs. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Castor oil‐based polyurethane–polyester nonwoven fabric composites: Mechanical properties,chemical resistance,and water sorption behavior at different temperatures

Castor oil‐based polyurethane (PU)–polyester nonwoven fabric composites were fabricated by impregnating the polyester nonwoven fabric in a composition containing castor oil and diisocyanate. The effects of different diisocyanates such as toluene‐2,4‐diisocyanate (TDI) and hexamethylene diisocyanate (HMDI) on the mechanical properties have been studied for neat PU sheets and their composites with polyester nonwoven fabric. Chemical resistance of the PU composites has been assessed by exposing the specimens to different chemical environments. Percentage water absorption of composites and neat PU sheets has been determined both at room temperature and in boiling water. Both TDI‐ and HMDI‐based PU composites showed a marginal improvement in tensile strength retention at 100°C heat ageing. Water sorption studies were carried out at different temperatures, viz, 30, 50, and 70°C, based on immersion weight gain method. From the sorption results, the diffusion (D) and permeation (P) coefficients of water penetrant have been calculated. Attempts were made to estimate the empirical parameters such as n, which suggests the mode of transport (non‐Fickian), and K, a constant which depends on the structural characteristics of the polymer in addition to its interaction in boiling water. The temperature dependence of the transport coefficients has been used to estimate the activation energy parameters for diffusion (E_D) and permeation (E_p) processes from Arrhenius plots. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Poly(styrene‐co‐butyl acrylate) latex‐reinforced polyester nonwoven fabric composites: Thermal and morphological studies

A series of thermoplastic composites were fabricated by impregnating the polyester nonwoven fabric in poly(styrene‐co‐butyl acrylate) latex having different monomer compositions of styrene and butyl acrylate viz., 100/0, 90/10, 80/20, 70/30, 60/40, and 50/50 weight by weight. Thermogravimetric analysis (TGA) of the composites was performed to establish the thermal stability and their mode of thermal degradation. From TGA thermograms, a slight improvement in thermal stability of the composites was noticed compared to polyester nonwoven fabric. Degradation kinetic parameters were obtained for the composites using Broido and Coats–Redfern methods. The activation energy (E_a) of the composites for the thermal degradation process lies in the range 7.1–261 and 60–264 kJ/mol for Broido and Coats–Redfern methods respectively. Morphology of the tensile‐fractured composites was studied using scanning electron microscopic technique. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Characteristics of the degradation and improvement of the thermal stability of poly(siloxane urethane) copolymers

This work investigates the characteristics of the thermal degradation of poly(ether urethane) (E‐PU) and poly(siloxane urethane) (S‐PU) copolymers by thermogravimetric analysis (TGA) and thermogravimetric analysis/Fourier transform infrared spectroscopy (TG–FTIR). The stage of initial degradation for E‐PU was demonstrated as a urethane‐B segment consisting of 4,4′‐diphenylmethane diisocyanate (MDI) and 1,4‐butanediol. Moreover, the urethane‐B segment in the copolymers had the lowest temperature of degradation (ca. 200°C). The degradation of E‐PU was determined by TGA and TG–FTIR analyses and had three stages including seven steps. Although the soft segment of S‐PU possessed the thermal stability of polydimethylsiloxane (PDMS), the unstable urethane‐B segment existed in S‐PU. Therefore, the initial degradation of S‐PU appeared around 210°C. The four stages of degradation of S‐PU involved eight steps, as revealed by TG–FTIR, which identified the main decomposition products: CO₂, tetrahydrofuran, and siloxane decomposition products. The imide group with high thermal stability was to replace the urethane‐B segment of S‐PU, which had the lowest thermal stability herein. The poly(siloxane urethane imide) (I‐PU) copolymer around 285°C exhibited a high initial temperature of degradation, and the initial degradation occurred at the urethane‐S segment consisting of MDI and PDMS. The degradation of I‐PU was similar to that of S‐PU and had four stages including six steps. Moreover, the degradation region of the imide group between 468 and 625°C was merged into the degradation stage of the siloxane decomposed products. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

蓖麻油作交联剂的聚氨酯弹性体的合成及性能

以不同摩尔比的四氢呋喃均聚醚（PTMG）和1,6-亚己基二异氰酸酯（HDI）合成聚氨酯（PU）预聚体,再分别用丁二醇（BD）、蓖麻油（CO）以及BD和CO混合物进行扩链交联,合成了一系列不同CO含量的PU.通过FTIR、AFM、拉伸实验和TGA,对不同硬段含量和CO含量PU的氢键化程度、相形态结构、力学性能和热性能进行了比较。结果表明,二异氰酸酯和扩链剂的种类及用量对PU的性能均有很大的影响。随着PU中二异氰酸酯用量的增加,其力学性能和热稳定性能提高。随着扩链剂中CO用量的增加,PU氨酯键的氢键化程度降低,其软、硬段的微相分离程度降低,导致其力学性能降低。但CO用量的增加会提高PU分子链的交联和支化,因而其热稳定性能得到提高。     

Multi-functional Polyester Hollow Fiber Nonwoven Fabric with Using Nano Clay/Nano TiO2/Polysiloxane Composites

Surface modification and property improvement of hollow polyester fiber nonwoven fabric is very important due to the application of substrate in the various fields. Here, nano clay, nano TiO₂ and polysiloxane softener as been applied on the hollow polyester fiber nonwoven fabric through conventional impregnation-dry-cure method in order to enhance the fabric properties. The alkaline hydrolysis of polyester was performed on the nonwoven surface to functionalize the fabric and increase the nanoparticles uptake. The nano clay was first dispersed by using nonionic dispersing agent, and then nano titanium dioxide dispersion was added dropwise to the prepared nano clay dispersion. Also, other dispersions were prepared with adding polysiloxane softener and polyurethane resin under sonication. The SEM images and EDX/XRD patterns indicated the presence of various applied particles on the surface of the fabric. Thermal gravimetric analysis was employed to investigate the thermal decomposition behavior of the treated samples. Self-cleaning properties of polyester nonwoven treated by TiO₂/nano clay/polysiloxane composite was followed by degradation of methylene blue under daylight irradiation at ambient temperature. It was found that nano clay/TiO₂/polysiloxane composite on the fabric surfaces improved self-cleaning property, thermal stability above 400 °C, and water absorption properties of the fabric.     

SMC中不饱和聚酯树脂增稠及贮存性能的研究

本文以甲苯二异氰酸酯（TDI）及其预聚物PU400、PU200为增稠剂对端羟基的不饱和聚酯进行增稠，通过树脂的粘度变化、螺线流动实验对这种新型增稠体系的增稠性能和片材的贮存稳定性进行了研究。并与以MgO为增稠剂的片材进行了对比研究，结果表明：（1）异氰酸酯预聚体的增稠性能优于异氰酸酯单体。（2）增稠剂PU400的质量百分数Wpu应该小于10％。在相同的－NCO浓度下，不饱和聚酯树脂的增稠速度随分子量的提高而加快；在273K下，不饱和聚酯树脂能在4天内完成增稠，在323K下，能在8小时内完成增稠。（3）聚酯片材贮存三个月后，由异氰酸酯增稠体系制备的片材的螺线长度，低于氧化镁增稠体系的下降幅度。     

Synthesis and characterization of polyurethane/poly(vinylidene chloride) interpenetrating polymer networks

A series of polyurethane (PU)/poly(vinylidene chloride) (PVDC) interpenetrating polymer networks (IPNs) were synthesized through variations in the amounts of the prepolyurethane and vinylidene chloride monomer via sequential polymerization (80/20, 60/40, 50/50, 40/60, 30/70, and 20/80 PU/PVDC). The physicomechanical and optical properties of the IPNs were investigated. Thermogravimetric analysis (TGA) studies of the IPNs were performed to establish their thermal stability. TGA thermograms showed that the thermal degradation of the IPNs proceeded in three steps. Microcrystalline parameters, such as the crystal size and lattice disorder, of the PU/PVDC IPNs were estimated with wide‐angle X‐ray scattering. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1375–1381, 2007     

Jute fabric reinforced engineering thermoplastic sandwich composites. I. The effect of molding time

Jute fabric‐reinforced sandwich composites were fabricated using engineering thermoplastics. The jute fabrics were precoated with thermosetting resin to improve their thermal resistance before molding of the composites. Thermal gravimetric analysis (TGA) studies revealed that the resin coated fabrics decomposed at higher temperature than the uncoated jute. The onset of degradation of the coated fibers also falls between that of jute fibers and the thermoset resins. This indicates the presence of good interfacial bonding between jute fibers and both resins. Isothermal TGA studies revealed that jute could withstand brief exposure to higher temperature at 270 and 290°C. The sandwich composites were fabricated at 270°C by compression molding for 1.5 and 3 min in each case, and then characterized by flexural, tensile and morphological studies, i.e., SEM and optical microscopy. The uncoated jute fabric yielded composites of superior mechanical properties even with 3 mins molding at 270°C which is close to the degradation temperature of uncoated jute fibers. This is an indication that it is feasible to prepare jute fiber filled engineering polymer composites provided the exposure time at high temperature during processing does not exceed 3 mins as determined by TGA isothermal studies. SEM studies revealed strong fiber/matrix interfacial bonding between jute and the thermoset resins while the inferior mechanical properties of the resin coated sandwich composites could be attributed to the poor interfacial bonding between the already cured thermoset coating and the matrix based on optical microscopy of the polished cross‐sections. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Impact of delignification on mechanical,morphological, and thermal properties of wood sawdust reinforced unsaturated polyester composites

Mechanical, morphological, and thermal properties of the raw and delignified wood sawdust (DWS) reinforced unsaturated polyester (UP) composites were evaluated. Composites were prepared using Resin Transfer molding technique by changing filler loading (5, 10, 15, and 20 wt%) for both raw and DWS reinforced UP. Mechanical (tensile and flexural), Fourier transform infrared spectroscopy (FTIR), morphological (scanning electron microscopy [SEM]) and thermal (thermogravimetric analysis [TGA]) properties were successively characterized. FTIR confirmed the removal of lignin from wood sawdust during the delignification process. The tensile strength, Young's modulus, and flexural strength values increased only up to 15% filler loading then decreased with increasing the filler. DWS reinforced composites had better mechanical properties compared to raw composites. SEM micrographs reveal that DWS reinforced composites have good compatibility with UP resin. According to TGA results, DWS reinforced composites showed enhanced thermal stability at the final decomposition stage above 400°C. J. VINYL ADDIT. TECHNOL., 24:185–191, 2018. © 2016 Society of Plastics Engineers     

Thermo‐physical,thermal degradation,and flexural properties of betel nut husk fiber reinforced vinyl ester composites

This study aims to investigate the thermo‐physical, mechanical, and thermal degradation properties of betel nut husk (BNH) fiber reinforced vinyl ester (VE) composites. These properties were evaluated as a function of fiber maturity, fiber content, and fiber orientation. Thermo‐physical properties were analyzed experimentally using a hot disk TPS method. The introduction of BNH was found to reduce the thermal conductivity of neat VE. The thermal conductivity and thermal diffusivity of BNH reinforced VE composites decreased with the increase in fiber content. Short fiber BNH reinforced VE composites showed the lowest thermal conductivity as compared to the unidirectional and random nonwoven composites. The TGA analysis shows lower resin transition peak for the BNH reinforced VE composites than the peak of neat VE. Fiber maturity had a notable effect on the flexural modulus of the BNH fiber reinforced VE composites. Incorporation of 10 wt% BNH fibers into the composite has increased the composites' flexural modulus by 46.37%. However, further increases in the fiber content reduced both flexural strength and modulus of the composites. POLYM. COMPOS., 37:2008–2017, 2016. © 2015 Society of Plastics Engineers     

Effect of polyethylene terephthalate fiber reinforced with non-hydrophilic nano-silica on the mechanical,thermic, and chemical shielding characteristics of saturated polyurethane composite

The research investigates the reinforcing effect of scrap polyethylene terephthalate (PET) fiber, non-hydrophilic nano-SiO₂(NS-972) and heat suppressing agents in saturated polyurethane (SPU) composites. PET fiber was obtained through industrial mechanical processing from scraped PET. Thermic and surface morphology of synthesized SPU composites was characterized by using scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Thermic characteristics of filled PU,NS-PET fiber (1.5%)-APM (1:1) (PU-NF1.5A) composite with (1:1) proportion of additive NS-PET fiber (0.5–2%) and halogen free fire-extinguishing additives APM (0–3%) were determined utilizing UL-94, TGA, critical oxygen index, and smoke density. The tensile properties of the composite improved to 42.27% (4.14 MPa) when the filler content was increased to 1.5%. The WCA, moisture permeability and chemical resistance analysis indicated that fabricated composite films with variable additive content had excellent hydrophobicity and improved resistance to water, humidity, and chemical resistance. TGA data shows the increased thermal resistance of reinforced PU composite is attributed to the increased thermal deterioration temperature, resulted to the higher thermic degradation temperature of the terephthalic and sebacic acids used in the synthesis of PU. Smoke producing capacity of composite PU-NF1.5A (0–3%) reduced from 82% to 52%. The LOI improved from 19 to 23 (−vol.%) at 3% APM additives.     

Thermal Stability and Flame Retardancy of Rigid Polyurethane Foams/Organoclay Nanocomposites

The thermal stability and flame retardancy of a new kind of rigid polyurethane (PU) foams/organoclay nanocomposites developed by our research group were investigated by using thermogravimetry analysis (TGA) and cone calorimeter test. Results indicate that compared with pure PU foams, rigid PU foams/organoclay composites show significantly enhanced thermal stability and flame retardancy. The reasons leading to the results were discussed in detail by relating with the morphology of the composites. The discussion suggests that the enhancement degree of thermal stability and flame retardancy of composites compared with that of PU foams coincides well with the sequences of gallery spacing of organoclay in the PU matrix.     

Thermal stability of radiation‐grafted and dyed poly(ethylene terephthalate) fabric

The effect of degree of grafting (GY) and degree of dye uptake on the thermal stability of polyethylene terephthalate (PET) fabric was studied using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and X‐ray diffraction analysis (XDA). TGA showed that the degradation process was composed of three overlapping stages. The first and second stages were studied in detail. Methacrylic acid (MAA)‐grafted PET fabric was dyed using Rhodamine Red (RR) and Astrazonrot Violet (AV) basic dyes. It was found that grafting deteriorated the thermal stability of both stages. The first stage showed the formation of two new steps at low and high temperatures. Both steps are heating rate and graft yield dependent. The deteriorating effect of grafting was followed by the changes in the kinetic parameters. AV dyeing of grafted samples accelerated the degradation of both stages whereas RR dyeing improved the thermal stability to reach that of ungrafted fabric. XDA showed that the crystalline nature of AV dye stuff is responsible for the rapid degradation in both stages via the introduction of highly incompatible crystalline phase in the polymer back bone, which resulted in the formation of internal stresses that enhanced the degradation process. DSC measurements supported TGA results. The improvement in the thermal stability by RR dyeing is attributed to the amorphous nature and the high thermal stability of the RR dye stuff. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101:1007–1020, 2006     

废旧聚酯纺织品的热降解动力学

通过分析废聚酯纺织品的组分、黏度、含水率,并与常规聚酯切片对比,证明其由纯聚酯纤维布料组成,黏度低而杂质含量高。在氮气气氛下采用热失重分析测试布泡料和常规聚酯切片的热降解参数,发现布泡料的起始分解温度和最大分解速率温度都低于常规聚酯切片。用Kissinger法分析常规聚酯切片和白布泡料的热降解动力学,样品的ln(β/T2max)和1000/Tmax之间均呈现良好的线性关系,说明Kissinger方程可以很好地表述其热降解过程。计算发现白布泡料的活化能和指前因子均低于常规聚酯切片。     

Studies on Acrylonitrile-Butadiene (NBR) Latex-Reinforced Jute Nonwoven Fabric Composites: Chemical Resistance,Mechanical Properties,and Water Absorption

Composites were fabricated by impregnating the jute nonwoven fabric in a bath of acrylonitrile-butadiene (NBR) latex. The effects of different pickup ratios (dry-to-dry weight) of jute nonwoven fabric to NBR latex viz., 1:0.5, 1:1, 1:1.5, 1:2, and 1:2.5 on the performance of composites have been studied. The fabricated composites have been evaluated for physico-mechanical properties and chemical resistance. Percent water absorption of composites has been determined both at room temperature and boiling water. Effects of different relative humidity on the equilibrium moisture content of the natural jute nonwoven fabric-NBR composites have been evaluated.     

Strategy for kinetic parameter estimation—Thermal degradation of polyurethane elastomers

The kinetics of the thermal degradation of polyurethane (PU) elastomers based on poly(ether polyol) soft segments and an aromatic type of diisocyanate were investigated by thermogravimetric analysis (TGA) under a nitrogen atmosphere employing four heating rates. The corresponding kinetic parameters of the two degradation stages were estimated by minimizing the output error functional and by the Kissinger method. In evaluating the kinetic parameters of the two‐step PU thermal decomposition, a differential thermogravimetry curve was applied as an objective functional in a regression procedure. Parameter estimation was obtained by minimizing the weighted quadratic output error functional with the modified Nelder–Mead simplex search algorithm. The confidence regions in the preexponential factor‐activation energy space were established for both the first and second stages of degradation. The effect of the molecular weight of the soft segment and the content of the hard segment on the activation energy of the degradation process was constructed by response surface methodology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 764–772, 2007     

Agent distribution and water remaining of polyester nonwoven fabrics after‐treated with polyurethane–citric acid

Polyester nonwoven fabric samples were used to treat with aqueous solutions of water‐soluble polyurethane (PU) containing the foaming agent, citric acid, or the mixtures of foaming agent and citric acid to examine the water remaining and the degradation of PU under the simulative condition of under ground. The results reveal that the viscosity of PU solutions could affect the values of pickup and add‐on. The water remaining values for PU containing citric acid are higher than those for PU containing the foaming agent and PU containing the foaming agent and citric acid. The pore structures, nonwoven construction, and the pores caused by the aggregation of PU within/on the treated nonwoven fabrics can affect the water remaining. From the observation of SEM and the comparison of FTIR, the degradation of water‐soluble PU resin is proved, which could form the rough porous surface of PU resin on the fiber surface as a factor improving the water remaining. The value of water remaining for PU containing citric after 60 weeks' treatment is significantly higher than the pristine nonwoven fabric (control). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 47–56, 2006     

Preparations and Properties of Waterborne Polyurethane / Nanosilica Composites

Summary Aqueous dispersion of polyurethane(PU) ionomers, based on poly(tetramethylene glycol) as soft segment, isophorone diisocyanate as diisocyanate, 1,4-butanediol as chain extender, dimethylol propionic acid as potential ionic center, triethylene tetramine as crosslinker, and triethyl amine as neutralizer, were reinforced with hydrophobic nanosilica to give waterborne PU/nanosilica composites. The reinforcing effects of nanosilica were examined in terms of mechanical, dynamic mechanical, and thermal properties together with water swell and transparency of the dispersion cast films. With the addition of nanosilica to PU, tensile modulus and strength increased, and the rubbery modulus increased in magnitude and extended to higher temperature, and these enhanced mechanical and thermal properties, together with increased swell resistance were obtained without scarifying the transparency of the films.